Ductile consolidated beryllium

ABSTRACT

A mass of consolidated beryllium particles is described having a ductility characterized by a tensile elongation of at least about 2 1/2 percent in all three orthogonal directions.

Unite States Patent Denny et a1.

[ Dec. 18, 1973 DUCTILE CONSOLIDATED BERYLLIUM Inventors: John P. Denny, Shillington; Robert C. Solbach, Reading; Pen George J. Jagaciak, Barrington, all of Pa.

Kawecki Berylco Industries, Inc., New York, NY.

Filed: Feb. 24, 1971 Appl. No.: 118,516

Assignee:

US. Cl 29/1825, 29/182, 29/192, 75/05 R Int. Cl B22f 3/00 Field of Search 29/185, 192; 264/111; 75/200, .5 R

References Cited UNITED STATES PATENTS 6/1967 Choh-Yi Ang et a1. 29/182 3,089,222 5/1963 Yans 29/182 OTHER PUBLICATIONS Beaver, W. W. Fabrication of Beryllium by Powder Metallurgy in Metal Progress, 65(4): p. 92-97, Apr. 1954.

Primary ExaminerCarl D. Quarforth Assistant ExaminerR. E. Schafer A mass of consolidated beryllium particles is described having a ductility characterized by a tensile elongation of at least about 2 /2 percent in all three orthogonal directions.

4 Claims, N0 Drawings DUCTILE CONSOLIDATED BERYLLIUM This invention relates to bodies of consolidated beryllium particles and, more particularly, to such bodies of exceptional ductility in all three orthogonal directions.

For many purposes in the fabrication of beryllium, including the production of ductile or formable beryllium sheet or extrusions, it is advantageous to start with a ductile consolidated mass of beryllium particles. However, consolidated masses of beryllium particles have heretofore exhibited the high degree of brittleness historically associated with all beryllium metal products.

It has been generally believed that the goal of less brittle beryllium could be reached by increasing the purity of beryllium. To a limited extent this has proven to be a fact, and by limiting the metallic impurities to 1 percent and the BeO content to less than 2 percent, there could be produced consolidated bodies of hot pressed beryllium with 1 percent elongation in each of the orthogonal directions. However, even when the total metallic impurities have been reduced to less than 1 percent and the beryllium oxide content has been reduced to about 1.5 percent or less, the consolidated bodies prepared from beryllium particles of this purity have exhibited only a small further gain in ductility.

We have now discovered that a consolidated beryllium body can be produced having a heretofore unattainable degree of ductility in all of its three orthogonal directons when the beryllium particles possess a specific characteristic. This characteristic involves the oxide content of a certain fraction of the finer particles in addition to the overall oxide content of the whole mass of particles. Thus, we have discovered that it is possible to obtain a ductile mass of consolidated beryllium particles having an apparent density of at least about 95 percent of theoretical density and a tensile elongation of at least about 2.5 percent in all three orthogonal directions when the particles of beryllium, prior to their consolidation, are predominantly of minus 200 mesh size including a significant portion of particles of minus 400 mesh size, the latter having a BeO content not substantially in excess of about 1.5 percent by weight prior to said consolidation.

Beryllium metal is most commonly obtained in the form of bead from a high temperature reduction of a beryllium halide, but sometimes also in the form of flake obtained by electrolysis of a fused salt bath. The bead or flake, plus optional scrap beryllium, is vacuum melted into an ingot which volatilizes some of the impurities in the metal. The resulting purified metal ingot is then run through a chipper which disintegrates the solid ingot into smaller chips, and then the chips, with or without the addition of other scrap chips of adequate purity, are comminuted to powder of sufficient particle fineness to permit its subsequent consolidation by hot pressing, but isostatic pressing, cold pressing and sin tering, resistance sintering, pressureless sintering, and the like. The resulting consolidated mass of beryllium particles can then be rolled into sheet or extruded into other shapes, but the formability of the sheet or extruded shapes, and the success with which the consolidated beryllium particles can be converted into such sheet or extrusions, is dependent upon the ductility of the consolidated mass of beryllium particles not only in one or two but in all three of its orthogonal directions We have found that the ductility of a mass of beryllium formed from beryllium particles, consolidated as previously described, is dependent not only upon its total beryllium oxide (BeO) content but especially upon the beryllium oxide content of a specific sizefraction of the beryllium particles. The comminuting of beryllium chip to the powder form causes only a relatively small increase in the BeO content of particles of a size greater than about 325 mesh (Tyler Standard). As the particles smaller than about 325 mesh are produced by, or are subjected to, comminution, their oxide content tends to increase under normal conventional comminuting conditions and rises nearly exponentially beginning with particles of about 400 mesh and smaller (i.e., with sub-sieve size). If, however, comminution is carried out under conditions limiting the BeO content of the particle size fraction of minus 400 mesh to a maximum of about 1.5 percent by weight, we have discovered that the consolidated beryllium body made from such a mass of beryllium particles has a tensile ductility of at least about 2.5 percent in all three or thogonal directions when the consolidated mass has an apparent density of at least about percent of theoretical density.

The beryllium chip from which the powder is made by comminution inevitably contains some beryllium oxide because of the normal oxide film which forms on the surface of beryllium exposed to the ambient atmosphere. This relatively small amount of beryllium oxide is desirable in the consolidated beryllium particles because it impedes and effectively prevents the growth of grains during processing at temperatures which exceed the normal grain-growth temperatures of beryllium and because these oxide particles act to pin dislocations in the beryllium and thereby strengthen the beryllium. However, pursuant to our invention, the comminution must be carried out under controlled oxidation conditions so as not to increase the oxide content of the ultimate fraction of particles of minus 400 mesh size. Such controlled-oxidation comminution can be achieved by air-blast, or other gas-blast, comminution of the type described in US. Pat. No. 1,875,531, or by comminu tion in other conventional impact or ball mills in which an inert atmosphere, preferably with a limited but controlled amount of oxidizing gas, is maintained.

ln the gas-blast impact method of comminution, the beryllium chips are carried by a stream of high pressure gas from an expansion nozzle and against a target of beryllium. The high speed of the chips hitting the target causes comminution of the chips to particles of the desired size and range distribution while the cooling effect of the expanding carrier gas, even in the case of air, prevents excessive oxidation of the comminuted particles. In the case of other comminution mills, such as conventional ball mills, control of oxidation of the comminuted particles can be effected by using an inert atmosphere such as nitrogen, argon or helium, with or without small contents of oxygen, or by using a carbon dioxide atmosphere. By any of these expedients, accordingly, the oxidation of the minus 400 mesh size fraction of the beryllium particles can be limited as aforesaid yet carry on each particle a thin surface film, of nearly molecular thickness, which is not increased significantly during subsequent consolidation in vacuum.

We can presently offer no exact explanation for the exceptional and uniform ductility of consolidated beryllium bodies having the aforesaid characteristics in the beryllium particles from which they are made. It has been observed, however, that under microscopic examination the mass of beryllium particles appears to be significantly more free of discrete accretions or platelets of beryllium oxide and other non-metallic compounds on the surfaces of the beryllium particles than do those masses of particles available and used heretofore. The lesser quantity of such accretions would make possible more effective metallurgical bonding of the particles to one another and would produce a consolidated mass less resembling a cermet composed of particles of beryllium metal and beryllium oxide. Tests on the particles of various sizes in the be ryllium powder consolidated pursuant to our invention show that bodies prepared frorn the particles of minus 400 mesh size are many times more ductile than smiliar bodies formed from conventional comminuted particles, and it is a possibility that these more ductile small particles in the consolidated beryllium mass of our invention, in bonding the larger particles, impart an overall increase in ductility in all three orthogonal directions which is characteristic of our ductile consolidated beryllium product from which more ductile wrought beryllium products, such as extrusions, forgings and sheet, can be producted than have been obtained heretofore.

We claim:

1. A ductile mass of consolidated beryllium particles,

said mass having an apparent density of at least about percent of theoretical density, and a tensile elongation of at least about 2.5 percent in all three orthogonal directons.

3. A wrought beryllium product obtained from the ductile mass of'claim 1. a

4. A mass of beryllium powder which, upon consolidation, will form a ductile mass of beryllium, said powder being composed essentially of particles of beryllium which, prior to consolidation, are predominantly of minus 200 mesh size and include a significant portion of particles of minus 400 mesh size, the latter having a BeO content not substantially in excess of about 1.5 percent by weight prior to said condolidation.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3,779,713 D ted December 18 1973 lnventofls) John P. Denny, Robert C. Solbach and George J. Jagaciak It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the title page, item [75] the inventorshi p should read .as follows "Inventors: John P. Denny, Shillington; Robert C. Solbach, Reading, Pa.; George J. Jagaciak, Barrington, R. l.-

Column 1, line 57, "but" should read --hot--. Column 3, line 17, "smiliar" should read vsi mila r--.

Signed and sealed this 20th day of August 197A.

(SEAL) Attest: I

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMIWDC 503764559 r u.s. eovsmmeur PRINTING OFFICE: I959 o-sse-aaa.

l UNITED STATES PATENT OFFl CE CERTIFICATE OF CORRECTION Patent No- 3,779,713 Dated December 18, 1973 Inventor) John Denny, Robert C. I Solbach and George J. Jagaciak It is certified that error appears in thejabove-identified patent and that said Letters Patent are hereby corrected as shown below:

In the title page, item [75] the inventorship should read as follows: l

"Inventor-s": John P. Denny, Shillington; Robert L C. Solbach, Reading, Pa.'; George J.

Jagaciak, Barrington, R. I.-

Column 1, line 57, "but" should read hot.' 60 1 1. ne -17 f'smiliar" sh u a c lr--- Signed and sealed this 20th day of August 197a.

(SEAL) Attest: I

MCCOY M. GIBSON, JR. C. MARSHALL DANN- Attesting Officer Commissioner of Patents 

2. A ductile mass of consolidated beryllium particles, said mass having an apparent density of at least about 95 percent of theoretical density and a tensile elongation of at least about 2.5 percent in all three orthogonal directions, the ductile mass being composed essentially of particles of beryllium which, prior to consolidation, were predominantly of minus 200 mesh size and included a significant portion of particles of minus 400 mesh size, the latter having a BeO content not substantially in excess of about 1.5 percent by weight prior to said condolidation.
 3. A wrought beryllium product obtained from the ductile mass of claim
 1. 4. A mass of beryllium powder which, upon consolidation, will form a ductile mass of beryllium, said powder being composed essentially of particles of beryllium which, prior to consolidation, are predominantly of minus 200 mesh size and include a significant portion of particles of minus 400 mesh size, the latter having a BeO content not substantially in excess of about 1.5 percent by weight prior to said condolidation. 